1. Field of the Invention
The present invention relates to a liquid discharging head provided on a liquid discharging apparatus such as an ink-jet recording apparatus which records a text and an image, and a method for producing the liquid discharging head.
2. Description of the Related Art
As an example of the liquid discharging apparatus, there is known an ink-jet recording apparatus which discharges an ink toward a recording medium to record a text, an image, etc. on the recording medium. The ink-jet recording apparatus includes an ink-jet recording head which is constructed by stacking an ink channel member having an inner space storing the ink and a piezoelectric element deformable with application of voltage. An adhesive used for adhering the channel member and the piezoelectric element with each other is required to have an ink resistance property so that the adhesive force (adhesive strength) of the adhesive does not lower even when the adhesive makes contact with the ink. From this viewpoint, conventionally, a thermo-setting adhesive (thermo-curable adhesive) containing an epoxy resin as a main agent is used in many cases. In the ink-jet recording head, the piezoelectric element is deformed to pressurize the inner space in which the ink is stored, thereby causing the ink to be discharged.
The adhesion by means of the thermo-setting adhesive is performed at a temperature higher than a curing temperature of the thermo-setting adhesive. Here, since the channel member has a thermal expansion coefficient greater than that of the piezoelectric element, the channel member is thermally expanded to an extent greater than the piezoelectric element under a high-temperature environment. In this state, the channel member and the piezoelectric element are adhered to each other with the thermo-curable adhesive. Afterwards, when the temperatures of the channel member and the piezoelectric element adhered to each other return each to a normal or room temperature, the channel member is contracted by a contraction amount greater than a contraction amount by which the piezoelectric element is contracted. Since the channel member and the piezoelectric element are adhered to each other, the piezoelectric element receives a reaction force as the channel member is contracted by the greater contraction amount. Namely, compressive stress is applied to the piezoelectric element when the temperature returns to the room temperature after the adhesion performed under the high temperature, which thus creates a state that after the adhesion, the stress applied to the piezoelectric element during the compression remains in the piezoelectric element. Since the remaining stress hinders the deformation of the piezoelectric element, the piezoelectric property of the piezoelectric element is consequently lowered.
Relating to this problem, Japanese Patent Application laid-open No. 2005-41053 describes that a low-thermal expansion material is used for the channel member, and that the difference between the thermal expansion coefficient of the channel member and the thermal expansion coefficient of the piezoelectric element is reduced to thereby lower the remaining stress generated in the piezoelectric actuator.